Is 1/2" ply too thin for this?

[KurtSchwind]

I'm essentially making a fancy crate (30" wide, 24" tall, 12" deep) that will hold laminated poster boards. The collection of poster boards is pretty heavy (maybe 50 lbs) and I'm wondering if 1/2" ply is enough or if I should just go with 3/4?

Attaching a sketchup of what I'm doing.

[Beechwood Chip]

My gut tells me that 1/2" over a 12" span will be OK.

Is this going to be moved around while loaded, or just sit in one place? How will it be used?

Your drawing shows a base much thicker than the sides. Is that a plinth, or solid?

I'd use dadoes for the floor, and rabbets reinforced with glue blocks or angle irons at the corners. Maybe pegged.

[KurtSchwind]

My gut tells me that 1/2" over a 12" span will be OK.

It'd be 1/2" over 30" across the front and back. I'm really starting to think that it'll be too thin. Or I could reinforce it but what's the point if I could just use 3/4.

Is this going to be moved around while loaded, or just sit in one place? How will it be used?

Your drawing shows a base much thicker than the sides. Is that a plinth, or solid?

I'd use dadoes for the floor, and rabbets reinforced with glue blocks or angle irons at the corners. Maybe pegged.

It shouldn't move[1]. And the base is 2 3/4" ply put together.

[1] "shouldn't" but if they want it to move, I might put casters on it. That's partly why I have such a thick base.

[Beechwood Chip]

It'd be 1/2" over 30" across the front and back. I'm really starting to think that it'll be too thin. Or I could reinforce it but what's the point if I could just use 3/4.

Think of a plank between two supports 12" apart, that's strong enough to support some load. Now, you put an identical plank next to the first plank, with the same load. You don't have to make the first plank thicker just because you put a second plank with a second load next to it. You can put 30 of these planks next to each other, or 100, and it still wouldn't change how string each plank needs to be.

That's why you look at the shortest distance between the supports.

3/4" inch will be stiffer and stronger. By all means, go with your gut, not mine. 1/2" will be strong enough, but might be a little bouncy.

[Renzo]

What's your motivation for wanting to go 1/2"

Do you already have it without having to go by more?

If you have to goto the store either way, why not go for 3/4 then there will be no issues for sure.

[KurtSchwind]

What's your motivation for wanting to go 1/2"

Do you already have it without having to go by more?

If you have to goto the store either way, why not go for 3/4 then there will be no issues for sure.

I have a bit of 1/2" ply but truth be told, I'll probably end up at a big-box buying more for this.

I guess my thought process was that I could keep the weight down a bit, but maybe that's faulting thinking.

[AMarshall]

My gut says the 1/2" would be fine. Remember that the back is supported on both sides and by the bottom as well. As long as the joints are strong, the back could really only bow out at the top. The front really isn't going to bow since it's only 12" tall. Finally, the 50 lbs is spread across the whole width, so there wouldn't be any great pressure in the middle anyway. Go for it.

[KRAM121881]

i just built somthing like this out of 1/2" plywood. It works just fine but as someone above stated, and I can confirm there is a little bounce in it on the long sides. It gets the job done for me, but if I were doing it again i would go with the 3/4. I had the 1/2" stock in the shop so that is what i used.

[KurtSchwind]

Thanks for the advice everyone. I think I'm going with 3/4 since it's going to be in a classroom setting. It should be able to withstand a bit more abuse.